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so while reading a interview with the creator of the sid chip, i remember him mentioning that there is a pin for processing external audio through the chip. He stated that no one ever used it. so i was wondering.... have any of you tried to do something with this guy? its pin 26.

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hardcore, Australia

I know the sammich sid has an audio in.

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Milwaukee, WI

AFAIK it is just used for filtering.  So I might be wrong but whenever there is an instance of filtering in anything on the C64 if you pump audio through that it will be filtered.  Lots of people do it wither their MSSIAH setups and stuff.

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prohphet64 mssiah uses it. So does hardsid big_smile

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New York City

It runs the external input through the SID filters.

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sweden

Is there any sid based synth that doesn't use it?

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apparently i am behind the times. Is I mean.... have any of u guys used the sid filter as an efx processor? How does it sound?

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England
wedanced wrote:

.... have any of you tried to do something with this guy? its pin 26.

I usually ground it, as it is floating as standard on a C64. Grounding it reduces noise, although it prevents the audio input from being used.

Last edited by InactiveX (Jul 3, 2011 5:57 pm)

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Matthew Joseph Payne

Couldn't you attach it to a switching 1/4" jack that grounds the pin when nothing is plugged in?

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England

Of course, but I've never really seen a need to have an audio in on the C64.

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New York City

Also: you could fry the chip plugging shit in so I never bothered with it.

Last edited by akira^8GB (Jul 4, 2011 1:49 pm)

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if you're a kickass coder you can use the filters with samples anyway

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Nomad's Land

yaaahh the famous vicious sid demo. do you know if the source code of the routine is available anywhere?

bw don't forget to check the best part of that demo: http://www.youtube.com/watch?v=ZW2XKSWUPLw

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Australia

Then there is this  ;-)

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that is pretty sweet.

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What you can do with audio-in signals in the SID:
The EXT-In Signal is mixed with the internal sound voices and through the main volume register and through the filters.

So, when you just want to use the SID with the external audio signal you can adjust the volume and filter it.
Is has a setting for high-pass, low-pass, band-pass filter and combinations of it. has a register for the resonance frequency and a register to set the q-factor of the resonance.

but that all theoretical things are maybe a little bit useless when it comes to the old generation of SID-chips. theire filters behave very weired with lots of distortion. people used it in their way with the games that it sounded good with the "originally not intended" distortion of that filters.
also different SID-chips from the same production behaved different cause of the production process that delivered not constant results for the analog parts on the chip.

so these filters are not something that made the c64 great for modifying external audio signals.
however, when you have the later models of the SID: 8580/6582 or 6581R4AR the filters work good and predictable - like the designer wanted them to behave at the first place (but did not have the time to correct it that way cause the c64 needed to be finished and sold!).

but is the SID-chip a worthy chip just for filters with a digital interface? i don't know the chips that are available for filtering, but i guess there are good chips available for that kind of task. i don't know about the ealy 80's - anyone?